1. Field of the Invention
The present invention relates to a transverse zooming lens set, and especially to a zooming lens set in which the focus change is performed without adjusting the longitudinal (optical axis) direction distance between lenses in the lens set.
2. Description of the Prior Art
In current camera, telescope and other photo lens systems, a zooming lens set can be adjusted to make the object being imaged appear gradually bigger or smaller so that it seems to be getting steadily closer or more distant. In these devices, by longitudinal movement of the lenses along the optical axis, the focus is changed for making up the images in different sizes. Changing focus is to adjust the distance between lenses or lens sets by moving the lenses or lens sets along the optical axis. However, the traditional way of changing focus is very difficult and complicated. One primary reason is that the relation between the track of the lenses with respect to the focus is nonlinear. Thus, a very precise guiding track (cam) is necessary for adjusting the relative distance between the lens sets. There are optic problems as well as mechanical difficulty in manufacturing a complete lens set with variable focus.